1. Field of the Invention
The present invention relates to an eccentric driving apparatus for causing a certain object to revolutionarily move without being associated with auto-rotational movement, and more specifically to an eccentric driving apparatus suitable for use in hardening equipment for cam shaft which carries out simultaneous hardening of the outer peripheral surface of each cam of a cam shaft having plural kinds of cams of different phases formed thereon.
2. Prior Art
A cam shaft used in an engine for an automobile has plural kinds of cams having different phases, and induction hardening is carried out on the outer peripheral surface of each cam. For achieving this induction hardening, a heating device equipped with a plurality of heating coils of circular shape which correspond to the respective cams is utilized. That is, a cam shaft is rotated in the state that a cam shaft is passed through the plurality of heating coils which are arranged in the direction of central line and the corresponding cams are positioned inside the respective heating coils, and whereby induction heating of the outer peripheral surface of each cam is effected simultaneously.
In conventional hardening equipment for a cam shaft, the plurality of heating coils are concentrically arranged, so that the center of the cam shaft corresponds to the center of the coils. Therefore, in the hardening of each cam, as shown in FIG. 6, the outer peripheral surface of each cam 11 of a cam shaft 10 is heated while being rotated inside a heating coil 21 in the state that the center O1 thereof corresponds to the center O2 of the heating coil 21, and subsequently cooled to complete hardening.
In such a way of hardening, however, a convex portion of the cam 11 always moves in the vicinity of the inner surface of the heating coil 21, which causes an essential disadvantage that the portion in question is hardened in larger depth than other portions.
For eliminating this disadvantage, the applicant of the present invention has developed such hardening technique that, as shown in FIG. 7, the center O2 of the heating coil 21 is made to be eccentric away from the center O1 of the cam 11 toward the convex side, and the heating coil 21 is revolved about the center O1 of the cam 11 in accordance with the rotation of cam 11, thereby hardening the outer peripheral surface of the cam 11 with a substantially uniform depth over the entire circumference (See Japanese Patent Application No. 11-319879 (1999) and Japanese Patent Application 2000-020417). As the hardening equipment for realizing the above technique, those shown in FIG. 8 or 9 have been suggested.
In the hardening equipment shown in FIG. 8, a plurality of heating devices 20, 20 corresponding to cam phases of the cam shaft 10 are provided. The plurality of heating devices 20, 20 are arranged on both sides of a hardening position of the cam shaft 10, respectively. Each heating device 20 has the heating coil 21 of circular shape which fits with the outside of the corresponding cam 11 of the cam shaft 10 and a transformer 22 for supplying the heating coil 21 with electric power, and the heating coils 21, 21 are made to be eccentric from the center O1 of the corresponding cams 11, 11 toward the convex side by a certain amount.
Each heating device 20 is revolved by an eccentric driving apparatus 30. The eccentric driving apparatus 30 has a support 31 for supporting the transformer 22, a bearing 32 attached on the bottom surface of the support 31, an eccentric cam 33 to be fitted with the bearing 32 and a rotation driving shaft 34 for driving the eccentric cam 33.
In the eccentric driving apparatuses 30, 30 disposed on both sides, the rotation driving shafts 34, 34 are driven by a common driving source 40. The eccentric cams 33, 33 are deflected in their rotation phases in accordance with the phase difference between the corresponding cams 11, 11 of the cam shaft 10.
In the hardening, the driving source 40 is actuated in accordance with the rotation of the shaft 10 to rotate the driving shafts 34, 34. In response to this, the heating devices 20, 20 revolve at a certain phase difference without auto-rotating. As a result, the heating coils 21, 21 revolve about the center O1 of the corresponding cams 11, 11 without being associated with auto-rotation.
To the contrary, in the hardening equipment shown in FIG. 9, the heating devices 20, 20 are driven by the eccentric driving apparatus 30, 30 of the biaxial driving system. That is, the eccentric driving apparatus 30 has two driving sources 35, 36 for linearly driving the heating device 20 in two directions perpendicular to the center line of the cam shaft 10, and the heating device 20 is caused to revolve by operation control of the driving sources 35, 36.
Comparing the hardening equipment shown in FIG. 8 and the hardening equipment shown in FIG. 9, the heating devices 20, 20 are the same between these equipments. However, the eccentric driving apparatuses 30, 30 are significantly different between these equipments. That is, in the hardening equipment shown in FIG. 8, the eccentric driving apparatuses 30, 30 are driven by the common driving source 40, while in the hardening equipment shown in FIG. 9, the eccentric driving apparatuses 30, 30 each need the two driving sources 35, 36, individually. Therefore, the former hardening equipment shown in FIG. 8 is much simpler in structure so that the cost thereof is low.
The eccentric driving apparatuses 30, 30 shown in FIG. 8, however, have a significant problem in the hardening operation as follows.
More specifically, in the case of carrying out hardening on the cam shaft 10, the cam shaft 10 is positioned at the hardening position while being passed through the heating coils 21, 21 aligned in the axial direction. In the eccentric driving apparatuses 30, 30 of the hardening equipment shown in FIG. 8, the amount of eccentricity is uniquely determined by the eccentric cams 33, 33 and hence the adjustment thereof is impossible, with the result that the heating coils 21, 21 are made to be eccentric fixedly in different directions in accordance with the phases of the cams 11, 11 of the cam shaft 10.
For this reason, it is impossible to effect the operation of zero recover for bringing the respective centers of the heating coils 21, 21 into correspondence with the respective centers O1 of the cams 11, 11, so that it is impossible to concentrically align the heating coils 21, 21. As a result, the positioning operation of the cam shaft 10 at the time of hardening operation becomes difficult and even becomes impossible when the amount of eccentricity of the heating coils 21, 21 is large. Furthermore, the amount of eccentricity of the heating coils 21, 21 is restricted to cause some troubles for uniform hardening of the respective outer peripheral surfaces of the cams 11, 11.
Incidentally, in the eccentric driving apparatuses 30, 30 of the hardening equipment shown in FIG. 9, the heating coils 21, 21 are easily recovered to the zero positions and concentrically aligned by controlling the driving sources 35, 36.
The present invention has made in consideration of the above problems, and an object of the present invention is to provide an eccentric driving apparatus having a simple structure and enabling arbitrary and simple adjustment of the amount of eccentricity.
An eccentric driving apparatus according to the present invention is an eccentric driving apparatus for revolving a certain object without being associated with auto-rotation, the eccentric driving apparatus comprising: a bearing for supporting the object, the bearing being supported so as to be movable in two directions perpendicular to the center of the revolution; a first rotation sleeve rotatably fitted to the inside of the bearing, having an inner peripheral surface inclined in one direction with respect to the center of rotation; a second rotation sleeve fitted to the inside of the first rotation sleeve so as to be movable with the same, having an outer peripheral surface inclined in one direction in correspondence with the inner surface of the first rotation sleeve; and a rotation driving shaft fitted to the inside of the second rotation sleeve so as to be movable with the same, wherein the first rotation sleeve and the second rotation sleeve are allowed to relatively move in the direction of the center of rotation, thereby configuring an eccentric cam unit having a variable amount of eccentricity.
Namely, in the eccentric driving apparatus according to the present invention, the inner peripheral surface of the first rotation sleeve is inclined in one direction, and the outer peripheral surface of the second rotation sleeve located inside the first rotation sleeve is inclined in one direction in correspondence with the inner peripheral surface of the first rotation sleeve. Owing to the inclination in one direction of the opposing peripheral surfaces, when the first rotation sleeve and the second rotation sleeve are relatively moved in the direction of the center of rotation, the outer peripheral surface of the first rotation sleeve is moved in parallel in the direction of inclination of the opposing peripheral surfaces with respect to the inner peripheral surface of the second rotation sleeve, so that the amount of eccentricity of the bearing with respect to the rotation driving shaft is adjusted to an arbitrary value including zero. In addition, the first rotation sleeve and the second rotation sleeve revolve while auto-rotating as a result of rotation of the rotation driving shaft, however, since the auto-rotation is not transmitted to the bearing, the bearing just revolves. As a consequence of this, the object can revolve without being associated with auto-rotation with an arbitrary amount of eccentricity including zero.
In the eccentric driving apparatus according to the present invention, it is also possible that at a plurality of positions in the axial direction of the rotation driving shaft, the eccentric cam unit comprising the bearing, the first rotation sleeve and the second rotation sleeve is provided. Furthermore, it is also possible that plural rotation driving shafts are arranged so as to be parallel with each other, and each rotation shaft is provided with the eccentric cam unit comprising the bearing, the first rotation sleeve and the second rotation sleeve.
The eccentric driving apparatus according to the present invention is particularly suitable for use in revolving a heating device used for simultaneous heating of the cams having the same phase in hardening equipment for a cam shaft which carries out hardening of the outer peripheral surface of each cam of a cam shaft on which plural kinds of cams having different phases are formed. In such a case, it is preferable that plural rotation driving shafts are arranged so as to be parallel with each other, and each rotation shaft is provided with the eccentric cam unit comprising the bearing, the first rotation sleeve and the second rotation sleeve. As a consequence, the heating device can be supported in a stable manner and stable revolution can be realized.